As a result of rigorous environmental regulations shifting towards zero-discharge, drilling wastes are the focus of attention in the oil and gas exploration industry. Drilling with oil-base mud (OBM) or synthetic-base mud (SBM) generates waste streams often referred to as “slop mud” or “slop water.” “Slop water” or “slop mud” are among the significant waste streams from exploration and development activities. Slop water or slop mud is a waste stream which is produced when an oil/synthetic/diesel-based drilling fluid becomes contaminated with water. These waste streams are byproducts of cleaning the drill floor, shaker room, pump room and other areas where spillage and interfaces during displacement occur. Contamination can also take place during boat cleaning operations, pit cleaning and other similar operations.
After contamination, the drilling fluid may contain 50 to 90% loosely emulsified water and 10 to 50% non-aqueous drilling fluid. This affects the properties of the drilling fluid by lowering the oil-water ratio (OWR), increasing viscosity, decreasing emulsion stability and ultimately forming an unusable drilling fluid. Hydrocarbon contamination renders these slops ineligible for overboard discharge. This unusable mud is typically sent for disposal or reconditioning. For operators, these volumes add up to enormous disposal expenses and represent a potentially expensive environmental issue.
In addition to good fluid design and solids-control equipment to help reduce the amount of waste generated, current separation processes exist to treat slop water/mud waste streams by breaking the weakly emulsified water phase and recovering the OBM/SBM so that mud can be reused without incurring the cost of expensive reconditioning and at the same time reduce the amount of waste generated. Currently, these slop wastes are pumped into treatment tanks where appropriate chemicals (demulsifiers) are added to separate the water from the drilling fluid. The demulsifier treatment concentration ranges from 2 to 4% by volume. The primary goal of this form of slop separation is to break only the weakly emulsified water phase and recover the oil/synthetic/diesel-based drilling fluid. The objective is to leave the OBM/SBM intact, so the mud can be reused with minimal reconditioning. The separation process lasts from 8 to 24 hours.
Once separation has occurred, the separated constituents (drilling fluid and water) are transferred to separate holding/treatment vessels. The recovered water is treated (flocculation and filtration) to local charge standards, if possible. If it cannot be discharged, it must be reused.
It would be an improvement to the art to have a system that includes a chemical technology that decreases the time required for phase separation and increases the quantity of water recovered. It would be a further improvement to the art to treat slop mud and clean/polish recovered water to make it dischargeable without further treatment. A shorter separation time could radically increase the quantity of slop processed. Increase in the phase separation efficiency would improve the drilling fluid OWR. Reducing the concentration of the water-soluble surfactant consumed would likewise reduce the organics in the recovered water and ease the downstream polishing of the water to meet discharge criteria. Too much shear can cause the separated water to re-emulsify back into the slop. A more effective surfactant/mixing technology would reduce the likelihood of re-emulsification. Current water treatment practices necessitate frequent changing of filter cartridges, which is expensive, labor intensive and time consuming.